Incoming schools chancellor Cathie Black raised hackles yesterday during an interview with WABC7, when she took aim at the city’s generous tenure policy for teachers. After slamming the system’s educator evaluation process, she added, “Nor can I imagine at age 25 or 24 saying to somebody: ‘You have lifetime guarantee for this position. Just show up every day.’ It’s inconceivable.” According to United Federation of Teachers President Michael Mulgrew, while principals can grant tenure to teachers after three years, it’s not quite a “lifetime guarantee.” “Clearly when they’re briefing her, they’re not telling her all the facts,” he told the Daily News. “Tenure only guarantees due process before they are fired, nobody is promised a job for life.” Black’s predecessor, Joel Klein, tried for years to kill a rule that ensures that during cutbacks, the least senior teachers are laid off first. Black is going to continue the fight, because she’s worried that the policy eliminates “younger, newer, fresher ideas.” No doubt Black will be surprised by how “fresh” senior teachers can get when you go after their goose that lays the golden eggs.